1. Field of the Invention
The present invention relates, in general, to cutting tools, and in particular, to a new and useful portable cutting tool and method which is capable of severing vessels while maintaining internal cleanliness conditions.
2. Description of the Related Art
U.S. Pat. No. 1,366,063 teaches a process for severing a bar utilizing a pair of wedge-shaped cutters located in the seam plane transverse to the axis of the bar. A first cut is made in the bar by the cutters to a certain depth at a high rate of speed. The bar is then rotated 90.degree. on its axis and subjected to a second cut for severing the bar.
U.S. Pat. No. 2,471,650 discloses two types of cutting tools having a rotatable cutting edge, a circular cutting tool having a saw-tooth cutting edge, and a cutting tool having a smooth cutting edge similar to a pizza cutter.
U.S. Pat. No. 3,958,732 teaches the breaking of steel rods into billets comprising cutting a circumferential notch into a surface of the steel rod. The rod is heated and quenched in order to develop a crack extending from the notch toward the center of the rod. A force is then applied to the rod at the notch which severs the rod.
U.S. Pat. No. 4,126,064 discloses a method for cutting a tube which utilizes a pair of cutting tools which provide a cut into the outside diameter of the tube to a certain depth. An annular bulge is formed at the inside diameter of the tube. The annular bulge is removed by a boring tool. The cutting tools are then reinserted into the original cut for cutting through the remaining pipe material.
U.S. Pat. No. 4,549,678 discloses a method for separating a cut tube end comprising a cutting tool which is used to cut a groove in the wall of a pipe. As a groove is cut circumferentially around the pipe by the cutter, a separator roller is inserted into the groove for breaking the thin metal remaining at the bottom of the groove which causes separating of the cut sections.
In the servicing of breeder reactor steam generators, a method of parting 1 1/2".phi..times.0.170" wall tubes without violating the cleanliness of the vessel interior was required. A tool was developed which fit inside the tube hole in the tubesheet and extended into the tube itself where it reduced the wall thickness where a parting cutter could sever the tube from the tubesheet. FIG. 1 depicts the tubesheet 10 and tube 12. A clean area 14 must be maintained in the steam generator. FIG. 2 depicts a relief cut 16 in the tube 12 and a tool drive mechanism 18 with cutting wheel 20. FIG. 3 depicts the parting tool 22 which severed the tube from the tubesheet.
This equipment was developed by B&W in the early 1980's
A completed tube bundle (tubesheet 10 and tubes 12) was inserted into a shell 24 in FIG. 4, and partially welded into position with approximately 3/8" of weld at 26. FIG. 4 depicts the shell/bundle assembly 28.
The alignment between sections violated the contract requirements. Therefore, the shell needed to be separated from the bundle assembly and repositioned. Cleanliness of the bundle was a paramount issue. Any violation of cleanliness would result in a major cleaning effort at a high cost in time and money.
A method of parting the pieces cleanly was required. The size of the repair operation and the different approach to the problem required a totally unique setup to part the vessels.